#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/bn.h>

int main()
{
        BN_CTX *r[3];
        BIGNUM *a,*b,*c,*d,*e;
        char s[512+1] = "20191308";
	    char t[512+1] = "20191303";
        char x[512+1] = "20191313";
	    char *x;
        r[0] = BN_CTX_new();
        a = BN_new();
        b = BN_new();
        c = BN_new();
        d = BN_new();
        e = BN_new();
        BN_dec2bn(&a, s);
        BN_dec2bn(&b, t);
        BN_dec2bn(&d, p);
        BN_mul(c, a, b, r[0]);//c=mul(a,b)
        BN_mul(e, c, d, r[0]);
        x = BN_bn2dec(e);
        puts(x);
        BN_free(a);
        BN_free(b);
        BN_free(c);
        BN_free(d);
        BN_free(e);
        BN_CTX_free(r[0]);
        free(x);
        return 0;
}